The Protein Functions that Keep Your Body Running

Proteins run nearly every metabolic process in your body, and they are part of the structure of every cell in your body. Here are a few examples.

Outwardly, the protein keratin makes up the outer layers of your skin (your epidermis), your nails, and your hair. One reason that you need to take in protein on a daily basis is because these external structures never stop growing. Whereas humans store fat and glucose in their bodies, the body really doesn’t have excess protein lying around.

So, when there is a protein deficit due to the fact that protein is needed constantly, protein is removed from places in the body where it is being used. For example, people with anorexia, who do not consume enough food, eventually start breaking down the muscle fibers, such as from their heart, when protein is needed.

Inside, muscle tissue is loaded with protein, and bones contain protein, too. Red blood cells contain hemoglobin, which is a compound made of heme (contains iron and carries oxygen) and globin (a protein). Immunoglobulins are protein structures created by your immune system that serve as antibodies to fight bacterial and viral invasions within your body.

Proteins also combine with other substances in the body to perform specific functions:

Lipoproteins are a combination of lipids (fats) and proteins that carry cholesterol throughout the body.

Glycoproteins are a combination of carbohydrates (sugars) and proteins that are found in cell membranes and mucous of the digestive tract, as well as in the extracellular matrix. They also play roles in the determination of blood type and cell recognition, which is important in the development of an embryo.

Phosphoproteins are a combination of phosphoric acid and proteins that create the main protein in milk: casein. The phosphorylation of proteins, especially enzymes, is a major way of regulating their activity.

One of the more important functions of proteins, however, is when they act as enzymes.

Enzymes are proteins that serve in chemical processes, such as those that occur during digestion. Enzymes serve as catalysts — that is, they help to speed up a reaction, but are not used up or changed during the reaction. There are six major types of enzymes:

Ligases, which join two molecules together

Lyases, which split two molecules apart

Hydrolases, which split two molecules apart when water is added

Isomerases, which create isomers (different chemical structures that have the same chemical formula)